Hormone and metabolite levels vary across the menstrual cycle. Sex hormones, like estrogen and progesterone, interact with the nervous system leading to inhibitory or excitatory effects that modify motor control. The purpose of this chapter is to summarize current knowledge regarding the effects of the endogenous hormonal changes characteristic of the menstrual cycle on the nervous system; the possible effects of oral contraceptives on the nervous system; and possible caveats related to these topics. In general, motor control and force production properties seem to be the highest in the late-follicular phase, following decrement in mid-luteal phase, and recovery in the late luteal through early-follicular phases, without effects from oral contraceptives. However, the modulation of the nervous system may also be muscle and location dependent since hormone levels and hormone receptors vary throughout the nervous system, increasing the complexity of the phenomenon. In addition, large variability between study designs and the paucity of existing studies makes it difficult to draw robust conclusions.